(botany, of various anatomical structures) Shaped like a kidney: in leaves, having the petiole attached at the notch; in seeds or spores, shaped generally like a kidney bean.

(zoology, of various anatomical structures) Shaped more or less like a human kidney in any of various ways, such as outline or contour, for example in the pupils of some species' eyes, the compound eyes of some insects, or the shapes of some bones or nodules.